The advent of solid cast detergent compositions has revolutionized the manner in which detergents are used and dispensed by those commercial and institutional entities which routinely use large quantities of cleaning solution. Prior to the advent of solid cast detergents, detergents were available in liquid, granular or pellet form. The solid cast form, such as those disclosed in Re. U.S. Pat. No. 32,763, Re. U.S. Pat. No. 32,818, U.S. Pat. Nos. 4,680,134 and 4,595,520, offered numerous unique advantages and quickly replaced a major portion of the conventional liquid, granular and pellet forms in the commercial and institutional markets.
The unique advantages offered by the solid cast forms of detergent include improved handling resulting in enhanced safety, elimination of component segregation during transportation and storage, increased concentration of active ingredients within the composition, and numerous others.
One method of manufacturing solid cast detergent compositions involves the steps of forming a homogenous melt of the various components, casting the molten melt into a mold, and solidifying the melt by cooling. For example, Fernholz et al., Reissue U.S. Pat. No. 32,763, describes a method of manufacturing a solid cast detergent composition which involves the steps of (i) forming an aqueous solution or dispersion of two hydratable chemicals, such as sodium hydroxide and sodium tripolyphosphate, (ii) heating the solution to a temperature of about 65.degree. to 85.degree. C. to form a heated solution, (iii) increasing the concentration of hydratable chemicals in the heated solution to produce a molten mixture which is liquid at the elevated temperature but solid at room temperature, and (iv) casting the molten mixture into molds for cooling and solidification to room temperature.
One difficulty encountered in the manufacture of solid cast detergent compositions by the molten process is the speed with which complete solidification of the cast composition can be achieved. It is understandably desirable to ensure that substantially the entire volume of a cast block of detergent composition is solid prior to effecting significant handling and/or transportation thereof in order to reduce the possibility that any remaining molten portion of the composition could be released and result in property damage and/or personal injury.
Generally, cast molten detergent compositions tend to cool and solidify from the exposed outer surfaces inward such that an outer crust usually forms on the cast detergent composition while the inner volume remains molten. This outer crust then tends to act as a insulating barrier and slows cooling of the remaining molten detergent composition. Because of this phenomena, it is generally accepted that, even though certain commercial and institutional users could benefit by using oversized blocks of solid cast detergent composition, the size of solid cast blocks of detergent composition formed by the molten process must be maintained below about 20 liters in order to prevent unreasonable delay in effecting complete solidification of the cast material.
In addition, the performance of solid cast detergent compositions is generally enhanced by the inclusion of one or more heat sensitive components such as tripolyphosphate detergent builders, chlorine bleaches, and enzymes. These heat sensitive components can be significantly degraded by extended exposure to the molten detergent composition.
Another drawback encountered in the manufacture of solid cast detergent compositions by the molten process is the need to employ a returnable/disposable mold within which the detergent may be cast, stored, transported, and dispensed. Disposable molds contribute to the growing problem of solid waste control while returnable molds are expensive to manufacture and cumbersome to handle.
Accordingly, a substantial need exists for a simple and relatively inexpensive process for producing oversized blocks of detergent compositions by the molten process which minimizes cooling time, reduces degradation of heat sensitive components, eliminates the need for environmentally harmful disposable receptacles and cumbersome returnable containers, and provides a generous exposed surface area available for dissolution by a dissolving fluid during dispensing.